Muchly changed and improved pprint.py:
- handles recursive data structures - formatting based on a PrettyPrinter object - allows a maximum nesting depth to be specified - provides safe repr()-like function which does not pretty-print
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Fred Drake
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Lib/pprint.py
247
Lib/pprint.py
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@ -1,7 +1,7 @@
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# pprint.py
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#
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# Author: Fred L. Drake, Jr.
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# fdrake@cnri.reston.va.us, fdrake@intr.net
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# fdrake@cnri.reston.va.us, fdrake@acm.org
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#
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# This is a simple little module I wrote to make life easier. I didn't
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# see anything quite like it in the library, though I may have overlooked
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@ -14,6 +14,13 @@
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Very simple, but useful, especially in debugging data structures.
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Classes
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-------
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PrettyPrinter()
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Handle pretty-printing operations onto a stream using a configured
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set of formatting parameters.
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Functions
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---------
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@ -21,123 +28,173 @@ pformat()
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Format a Python object into a pretty-printed representation.
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pprint()
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Pretty-print a list, tuple or dictionary.
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Pretty-print a Python object to a stream [default is sys.sydout].
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Constants
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---------
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INDENT_PER_LEVEL
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Amount of indentation to use for each new recursive level. The
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default is 1. This must be a non-negative integer, and may be set
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by the caller before calling pprint().
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MAX_WIDTH
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Maximum width of the display. This is only used if the
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representation *can* be kept less than MAX_WIDTH characters wide.
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May be set by the user before calling pprint() if needed.
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saferepr()
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Generate a 'standard' repr()-like value, but protect against recursive
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data structures.
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"""
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INDENT_PER_LEVEL = 1
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MAX_WIDTH = 80
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from types import DictType, ListType, TupleType
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def pformat(seq):
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"""Format a Python object into a pretty-printed representation.
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The representation is returned with no trailing newline.
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"""
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import StringIO
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sio = StringIO.StringIO()
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pprint(seq, stream=sio)
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str = sio.getvalue()
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if str and str[-1] == '\n':
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str = str[:-1]
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return str
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try:
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from cStringIO import StringIO
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except ImportError:
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from StringIO import StringIO
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def pprint(seq, stream=None, indent=0, allowance=0):
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"""Pretty-print a list, tuple, or dictionary.
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def pprint(object, stream=None):
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"""Pretty-print a Python object to a stream [default is sys.sydout]."""
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printer = PrettyPrinter(stream=stream)
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printer.pprint(object)
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seq
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List, tuple, or dictionary object to be pretty-printed. Other
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object types are permitted by are not specially interpreted.
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stream
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Output stream. If not provided, `sys.stdout' is used. This
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parameter must support the `write()' method with a single
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parameter, which will always be a string. It may be a
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`StringIO.StringIO' object if the result is needed as a
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string.
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def pformat(object):
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"""Format a Python object into a pretty-printed representation."""
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return PrettyPrinter().pformat(object)
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Indentation is done according to `INDENT_PER_LEVEL', which may be
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set to any non-negative integer before calling this function. The
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output written on the stream is a perfectly valid representation
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of the Python object passed in, with indentation to assist
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human-readable interpretation. The output can be used as input
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without error, given readable representations of all elements are
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available via `repr()'. Output is restricted to `MAX_WIDTH'
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columns where possible.
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"""
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if stream is None:
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import sys
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stream = sys.stdout
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def saferepr(object):
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"""Version of repr() which can handle recursive data structures."""
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return _safe_repr(object, {})
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rep = `seq`
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typ = type(seq)
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sepLines = len(rep) > (MAX_WIDTH - 1 - indent - allowance)
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if sepLines and (typ is ListType or typ is TupleType):
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# Pretty-print the sequence.
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stream.write(((typ is ListType) and '[') or '(')
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class PrettyPrinter:
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def __init__(self, indent=1, width=80, depth=None, stream=None):
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"""Handle pretty printing operations onto a stream using a set of
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configured parameters.
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length = len(seq)
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if length:
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indent = indent + INDENT_PER_LEVEL
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pprint(seq[0], stream, indent, allowance + 1)
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indent
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Number of spaces to indent for each level of nesting.
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if len(seq) > 1:
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for ent in seq[1:]:
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stream.write(',\n' + ' '*indent)
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pprint(ent, stream, indent, allowance + 1)
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width
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Attempted maximum number of columns in the output.
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indent = indent - INDENT_PER_LEVEL
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depth
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The maximum depth to print out nested structures.
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stream.write(((typ is ListType) and ']') or ')')
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stream
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The desired output stream. If omitted (or false), the standard
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output stream available at construction will be used.
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elif typ is DictType and sepLines:
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stream.write('{')
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"""
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assert (not depth) or depth > 0, "depth may not be negative"
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assert int(indent) or 1
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assert int(width) or 1
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self.__depth = depth
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self.__indent_per_level = indent
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self.__width = width
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if stream:
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self.__stream = stream
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else:
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import sys
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self.__stream = sys.stdout
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length = len(seq)
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if length:
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indent = indent + INDENT_PER_LEVEL
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items = seq.items()
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items.sort()
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key, ent = items[0]
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rep = `key` + ': '
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def pprint(self, object):
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self.__stream.write(self.pformat(object) + "\n")
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def pformat(self, object):
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sio = StringIO()
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self.__format(object, sio, 0, 0, {}, 0)
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return sio.getvalue()
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def __format(self, object, stream, indent, allowance, context, level):
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level = level + 1
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if context.has_key(id(object)):
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object = _Recursion(object)
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rep = self__repr(object, context, level - 1)
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objid = id(object)
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context[objid] = 1
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typ = type(object)
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sepLines = len(rep) > (self.__width - 1 - indent - allowance)
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if sepLines and typ in (ListType, TupleType):
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# Pretty-print the sequence.
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stream.write((typ is ListType) and '[' or '(')
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length = len(object)
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if length:
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indent = indent + self.__indent_per_level
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pprint(object[0], stream, indent, allowance + 1)
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if len(object) > 1:
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for ent in object[1:]:
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stream.write(',\n' + ' '*indent)
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self.__format(ent, stream, indent,
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allowance + 1, context, level)
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indent = indent - self.__indent_per_level
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stream.write(((typ is ListType) and ']') or ')')
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elif sepLines and typ is DictType:
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stream.write('{')
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length = len(object)
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if length:
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indent = indent + self.__indent_per_level
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items = object.items()
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items.sort()
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key, ent = items[0]
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rep = self.__repr(key, context, level) + ': '
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stream.write(rep)
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self.__format(ent, stream, indent + len(rep),
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allowance + 1, context, level)
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if len(items) > 1:
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for key, ent in items[1:]:
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rep = self.__repr(key, context, level) + ': '
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stream.write(',\n' + ' '*indent + rep)
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self.__format(ent, stream, indent + len(rep),
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allowance + 1, context, level)
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indent = indent - self.__indent_per_level
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stream.write('}')
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else:
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stream.write(rep)
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pprint(ent, stream, indent + len(rep), allowance + 1)
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del context[objid]
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if len(items) > 1:
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for key, ent in items[1:]:
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rep = `key` + ': '
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stream.write(',\n' + ' '*indent + rep)
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pprint(ent, stream, indent + len(rep), allowance + 1)
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def __repr(self, object, context, level):
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return _safe_repr(object, context, self.__depth, level)
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indent = indent - INDENT_PER_LEVEL
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stream.write('}')
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def _safe_repr(object, context=None, maxlevels=None, level=0):
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level = level + 1
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typ = type(object)
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if not (typ in (DictType, ListType, TupleType) and object):
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return `object`
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if context is None:
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context = {}
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else:
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stream.write(rep)
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if context.has_key(id(object)):
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return `_Recursion(object)`
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objid = id(object)
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context[objid] = 1
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if typ is DictType:
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if maxlevels and level >= maxlevels:
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s = "{...}"
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else:
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items = object.items()
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k, v = items[0]
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s = "{%s: %s" % (_safe_repr(k, context), _safe_repr(v, context))
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for k, v in items[1:]:
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s = "%s, %s: %s" \
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% (s, _safe_repr(k, context), _safe_repr(v, context))
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s = s + "}"
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else:
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s, term = (typ is ListType) and ('[', ']') or ('(', ')')
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if maxlevels and level >= maxlevels:
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s = s + "..."
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else:
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s = s + _safe_repr(object[0], context)
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for ent in object[1:]:
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s = "%s, %s" % (s, _safe_repr(ent, context))
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s = s + term
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del context[objid]
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return s
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# Terminate the 'print' if we're not a recursive invocation.
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if not indent:
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stream.write('\n')
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class _Recursion:
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# represent a recursive relationship; really only used for the __repr__()
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# method...
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def __init__(self, object):
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self.__repr = "<Recursion on %s with id=%s>" \
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% (type(object).__name__, id(object))
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def __repr__(self):
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return self.__repr
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